Genetics of Alzheimer’s Disease
Apolipoprotein E is involved in injury repair and transporting fats between brain cells. There are three main forms or alleles of APOE– APOE e2, APOE e3 and APOE e4. Individuals with one copy of the APOE e4 have three times the risk of developing late-onset Alzheimer’s, while those with two copies of APOE e4have 10 – 15 times the risk. APOE e2 appears to be protective against Alzheimer’s. Genome-wide association studies have recently identified several other genes that may also be linked to late-onset Alzheimer’s disease. These include CLU (regulates the clearance of amyloid-beta), CR1 (controls brain inflammation), and PICALM (helps neurons communicate). None of these other genes influence the risk of Alzheimer’s as much as the APOE e4 allele.
Other Risk Factors for Alzheimer’s Disease
Although the presence of the APOE e4 allele is strongly associated with an increased risk of Alzheimer’s, current research shows that several other factors may also play a role. There appears to be a link between cognitive decline (e.g. dementia) and vascular conditions (e.g. heart disease) and metabolic conditions (e.g. diabetes). Ongoing research is investigating whether reducing the risk factors for these other diseases will also reduce the risk of Alzheimer’s.
There are six important factors that have been associated with staying healthy as people age. These are a nutritious diet, physical activity, social engagement, mental stimulation, adequate sleep and good stress management. These same factors may also help reduce the risk of Alzheimer’s disease and other forms of dementia.